The shrinkage issue has posed a significant challenge for the practical application of biodegradable foam materials. The varying temperature-pressure mode (VT-PM) was adopted to fabricate poly (butylene adipate-butylene terephthalate) (PBAT)/Polybutylene succinate (PBS) foams. Foam shrinkage was significantly improved by the synergistic effect of temperature and pressure, and the shrinkage resistance mechanism was investigated by analyzing the cell structure. The crystallization behavior of PBS was investigated using differential scanning calorimetry (DSC) and polarized optical microscope (POM). Small size PBS crystals were obtained during the temperature change process, and the heterogeneous nucleation of PBS crystals increased the foaming expansion ratio. It was also found that the thick cell wall was able to act as a skeleton to support the structure of large cell size (>100 μm) foams, ensuring larger compression stress and modulus.
The synthesis of very thin Ag nanowires in the presence of Br− ions is typically accompanied by the generation of a huge amount of Ag nanoparticles. Herein, we report a method to suppress the homogeneous nucleation of Ag seeds in the growth process of Ag nanowires, hence dramatically enhancing the purity of the synthesized very thin Ag nanowires. These Ag nanowires having a diameter approaching 20 nm and an aspect ratio larger than 1500, as well as an ultra-low particle impurity level of 5.5% are directly used after simple water washing to form transparent conductive films with much improved optical and electrical properties, which have great potential for high-end applications including touch panels.
Near-critical/supercritical fluids have been widely proposed in material process, energy conversion and chemical engineering, etc. The present study is focused on the near-critical CO2 Poiseuille Rayleigh-Benard convective flow in microchannels. Careful numerical procedures are carried out by compressible Navier-Stokes equations, coupled energy and near-critical CO2 fluid state equations. In the physical model, sudden application of boundary heat fluxes in the boundaries is assumed. The flow and heat transfer characteristics of such Poiseuille Rayleigh-Benard configuration in microscales are systematically explored. For the convection onset, strong near-critical vortex flows are found for a relative wide range of initial and input conditions in microchannels. It is found that typical near-critical thin, hot boundary layer (HBL) plays critical role in the basic stability evolution process. The hot boundary layer formation process and the characteristics of the transition phenomena, convection structure, heat transfer behaviors as well as future development are also presented in this paper. It is hoped that this study can contribute to near-critical hydrodynamics in microscales.
Layered double hydroxides (LDHs), either having nitrate counter anions or intercalated with organic molecules, have been for the first time partially exfoliated in dimethyl sulfoxide (DMSO) to form a transparent suspension. Atomic force microscopy (AFM) images showed that both the lateral size and the thickness of the LDH nanoplatelets were decreased after the exfoliation. The organic-LDHs maintained their intercalation characteristics, i.e. the thermal stability improvement of the incorporated organic anions, after the exfoliation in DMSO. Transparent ethylene-vinyl alcohol copolymer (EVOH) nanocomposite films containing partially exfoliated LDHs intercalated with UV absorbers were prepared using DMSO as the processing solvent. As the first reported example of a highly transparent LDH/polymer composite, the obtained composite film had a visible light transmittance of 90% (comparable to that of the pure matrix), was flexible and exhibited an excellent UV-shielding capability and thermal stability.
In article number 1907029, Jianying Huang, Jun Hu, Yuekun Lai, Yuxin Tang, and co-workers reveal a correlation between the oxygen evolution reaction overpotential and the cobalt-based electrode composition in an electrospinning “Microparticles-in-Spider Web” superstructure electrode, leading to remarkable electrocatalytic activity.
Abstract The development of aqueous metal‐ion batteries has attracted great attention due to their relatively low cost and high safety levels. However, their practical applications are hindered by the ease at which their aqueous electrolytes freeze. Inspired by the antifreezing properties of salts and alcohol cryoprotective agents, a “two‐in‐one” cryoprotective agent, hydroxyl‐functionalized poly(ionic liquid) (PIL‐OH)‐based hydrogel electrolyte for aqueous lithium‐ion batteries (ALIBs) is developed. The synergy of both ionic hydration and hydrogen bond interactions between the PIL‐OH and water molecules impairs the hydrogen‐bond networks of water and depresses the freezing point of water below −80 °C. Benefiting from exceptional ultralow temperature tolerance, the prepared PIL‐OH hydrogel exhibits a highly enhanced low temperature adaptability and a high ionic conductivity of 0.08 mS cm −1 at −80 °C. The PIL‐OH hydrogel‐based flexible ALIBs exhibit high flexible durability and good cycling stability with 93% capacity retention over 200 cycles at −80 °C. The PIL‐OH hydrogel report herein opens up new opportunities for practical applications of wearable and flexible aqueous batteries at ultralow temperature environments, such as the North and South Poles.
Abstract A microwave assisted polyol process accomplished within 10 min was developed for synthesis of superparamagnetic Fe 3 O 4 nanoparticles (MNPs) with well controlled size between 2 and 6 nm. Effects of reaction time and temperature on the size of the MNPs were investigated through transmission electronic microscope, x-ray diffraction pattern, thermogravimetic and magnetic analysis. The results indicates that longer reaction time or higher temperature lead to formation of MNPs with larger size. As a proof-of-concept, the MNPs were utilized as peroxidase and their activity was also investigated. Oxidation of typical substrate, 3, 3’, 5, 5’ -tetramethylbenzidine, can be proceeded by using the MNPs as artificial mimic enzyme. The MNPs display the maximal catalyzed activity under the optimum condition as pH = 3.5, 40 °C and concentration of TMB and H 2 O 2 with 120 and 110 mmol·l −1 , respectively. This work provides a new way for fast synthesis of MNPs, which are of potential application in artificial mimic enzyme.
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